GB1581511A - Method of manufacturing a plastics record carrier having astratified structure as well as a device for carrying out the method - Google Patents

Description

PATENT SPECIFICATION

( 11) 1 581 511 ( 21) Application No 9551/78 ( 31) Convention Application No.

7 702 702 tn ( 22) Filed 10 March 1978 ( 32) Filed 14 March 1977 in Netherlands (NL) Complete Specification published 17 Dec 1980

INT CL 3 B 29 D 17/00 Index at acceptance B 5 A 1 R 214 H 1 R 314 C 1 F 1 R 418 20 N 2 20 T 1 2 E 12 A 2 F 1 2 F 26 A 2 ( 54) METHOD OF MANUFACTURING A PLASTICS RECORD CARRIER HAVING A STRATIFIED STRUCTURE AS WELL AS A DEVICE FOR CARRYING OUT THE METHOD ( 71) We, N V PHILIPS' GLOEILAMPENFABRIEKEN, a limited liability Company, organised and established under the laws of the Kingdon of the Netherlands, of Emmasingel 29, Eindhoven, the Netherlands do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:

The invention relates to a method of manufacturing a plastics record carrier of the kind having a stratified strucutre in which a layer of a moulding resin in a fluid form is provided on a mould surface having an information track thereon, a flexible substrate is provided on the layer of moulding resin, the layer of resin is cured and the assembly of substrate and attached layer of cured resin is removed from the mould.

Such a method is described in Netherlands Patent Application 7,411,707 (United Kingdom No 1 493 113) laid open to public inspection and is described in detail therein with reference to Figure 5 B According to this known method the whole surface of the mould is provided with the liquid moulding resin and subsequently the substrate is provided over the layer of moulding resin by means of a cylindrical roller Of course, the thickness of the layer of moulding resin is influenced and adjusted by the pressure with which the cylindrically curved substrate is pressed on the moulding resin The method is less suitable for use in a larger scale production process In addition the method has the principal disadvantage that, by using a cylindrical pressure roller, the layer of resin deformed in this manner shows differences in thickness in directions at right angles to and parallel to the cylinder axis of the pressure roller.

The information track present in the mould and adopted by the resin is as a rule in the form of a spiral or otherwise consists of concentric circles Said information track is scanned rotationally symmetrically in which speeds of rotation of the record carrier in the order of 1500 rpm are realized.

This relates to record carrier containing very 50 refined video information, otherwise known as the so-called video discs.

We have discovered that the layer of resin by means of a cylindrical roller has for the result that the finished product of scanning 55 shows two inevitable errors with every revolution At the above mentioned rotation speed this leads to 3000 disturbances per minute, which means an interference signal of 50 Hz 60 We have furthermore discovered that the layer of resin, with its information track has to be built up in the same manner as it is scanned and read afterwards in the reproduction apparatus, that is, in a rotationally 65 symmetrical build-up.

According to the present invention there is provided a method of manufacturing a plastics record carrier having a stratified structure in which a layer of moulding resin 70 in liquid form is provided on a surface of a mould having an information track thereon, a flexible substrate is provided on the layer of the moulding resin, the layer of resin is cured and the assembly of substrate and 75 cured layer of resin connected thereto is removed from the mould characterized in that the flexible substrate which has been or is in the process of being vaulted spherosymmetrically, is pressed against the 80 moulding resin which is provided centrally on the mould, the moulding resin thereby being rolled out over the mould surface with a circular fluid front and the vaulted substrate thereby being deformed to finally form 85 a plane surface, the moulding resin being cured and the assembly of substrate with attached layer of cured resin being removed from the mould.

In one embodiment of this method, when 90 ( 33) ( 44) ( 51) ( 52) 1 581511 the circular fluid front of the moulding resin is approaching the edge of the mould and the spherosymmetrically vaulted substrate is nearly redeformed to form a plane surface, the substrate is uncoupled from the pressure force so that the substrate pushes the fluid front towards the edge of the mould and engages the layer of resin without stress.

It will be obvious that a substrate which engages the layer of resin without stress will provide, after curing of the layer of resin, a record carrier having no or only small internal stresses as a result of which the possibility of deformation and possibly modulation of the stored information associated therewith is minimized.

The resulting plastics record carrier, after separation from the mould, also has a similar smoothness to that of the mould If desired, one may start the method by using a substrate which is not perfectly planar or flat and from it a perfectly planar or flat plastics record carrier may be obtained, provided the mould is planar or flat.

In a further embodiment of the method, the spherosymmetrically vaulted substrate is pressed against the moulding resin which has been deposited centrally on the mould in the form of a ring According to this embodiment of the method, record carriers, for example video discs, can be manufactured in which no layer of resin is present in the central portion Said portion may be used, for example, for providing a label.

In a further elaboration of the lastmentioned embodiment, a spherosymmetrical substrate is used which has a central aperture, the diameter of the aperture corresponding to or being smaller than the inside diameter of the annular layer of resin deposited on the mould The aperture present in the resulting record carrier may serve to centre the record carrier around a centring pin present in the reproduction apparatus.

A spherosymmetrically vaulted substrate is used in the method according to the invention In order to realize the spherosymmetrical shape of the substrate a plane substrate, which is in the form of a circle or ring, may be by flexibly suspended or supported along its whole circumference and then to provide a gas pressure which is different on both sides of the substrate.

According to a further embodiment of the method the difference in gas pressure may be varied The gas pressure may also form the force with which the spherosymmetrically vaulted substrate is pressed against the moulding resin.

Conventional polymerisable moulding resins may be used in the method according to the invention, for example the thermo setting urethane resin provided with a catalyst as stated in the above-mentioned Netherlands Patent Application 7,411,707 (U.K No 1 493 113) A radiation curable moulding resin may be used which is exposed via the substrate after has been rolled completely over the mould 70 Very suitable, radiation-curable moulding resins are described in our copending U K.

Patent Application No 42482/77 (Serial No 1 579 709) Such readily usable moulding resins comprise low-molecular monom 75 ers and/or oligomers which contain on an average 25-70 % by weight of saturated hydrocarbon groups and/or phenyl groups; they, furthermore are aprotic and have an average functionality as regards unsatura 80 tion which lies between the values 2 and 6.

Mixtures of low-molecular mono-, di-, trior tetra ester of acrylic as low viscosity liquids acid are used to which a photosensitive catalyst, for example an aromatic car 85 bonyl compound, for example benzoinisobutyl ether, may be added.

Examples of acrylic acid esters are 2-ethylhexylacrylate, ethylacrylate, phenylacrylate, 2-ethyoxyethylacrylate and 90 octadecylacrylate.

The mould used in the method may be a mould of which at least the surface comprising the information track is manufactured from metal 95 A very suitable mould is a mould manufactured from nickel as described, for example in United Kingdom Patent No.

1 447 066 The mould may have on its side remote from the information track a plane 100 stiffening plate, for example, an aluminium plate having a thickness of 1 to 10 mm.

The above-described, radiation-curable moulding resin does not adhere to the metal mould after curing but can readily be 105 detached from the mould A separate release agent is not necessary and is, in general, not desired because the transfer of information from the mould to the moulding resin should be as accurate as possible 110 A plastics plate is used as a substrate which has a thickness between 100 gtm and 1.5 mm When radiation-curable moulding resins are used, the substrate should be pervious to the radiation used, for example 115 ultra-violet light Suitable plastics are, for example, polyvinylchloride, copolymeric vinylchloride vinyl acetate, polycarbonate, polyester, polymethylmethacrylate and polystyrene The above-mentioned mould 120 ing resins readily adhere to the said substrates If desired the adhesion may be improved by chemically roughening the substrate with, for example, chloroform or providing it with an adhesion-improving top 125 layer For example, polymethylmethacrylate, such as, plexiglass may be provided with a top layer of polyvinylchloride/acetate.

The invention also relates to a device for 130 1 581 511 carrying out the method according to the invention of the kind which comprises a holder for the flexible substrate which holder if desired, having a connection for a pump, a support plate for the mould, as well as a source of power to move the holder or part of the holder relative to the support plate.

The aforesaid device is known from German Patent Specification 1,094,996, wherein there is disclosed a press for gramophone records in which at least one of the two press moulds is provided with a flexible diaphragm, the edge portion of which is clamped between the press mould and a pressure ring connected to the mould(s) by a screw joint The press mould has a pressure line through which liquid is pressed between the press mould and the diaphragm and consequently the diaphragm is deformed to become convex This known device is not suitable for carrying out the method according to the invention and has inter alia the disadvantage that the diaphragm cannot easily be removed from the press mould In this case it is to be noted that in the method according to the present invention the flexible substrate has to be removed from the mould together with the cured layer of moulding resin The substrate forms part of the record carrier so that a separate flexible substrate is needed for each plastics record carrier to be produced In the device known from German Patent Specification

1,094,996 the diaphragm which does not form part of the record disc to be produced is permanently connected to the press mould and serves to expel the air present between the press mould and the disc to be pressed.

According to the present invention there is provided a device for carrying out the method of the invention, in which the device comprises a holder for the flexible substrate said holder, if desired having a connection for a pump, a support plate for the mould as well as a power source to move the holder or part of the holder relative to the support plate characterised in that the holder comprises an elastically deformable cylindrical collar which at its annular end face remote from the holder comprises means to connect the substrate to the said collar along the circumference in a detachable and air-tight manner.

In one embodiment of the device for carrying out the method the end face of the collar comprises one or more vacuum grooves in which a sub-atmospheric pressure can be generated so that the substrate is sucked against the collar.

In this embodiment of the device the substrate can be uncoupled from the holder in a very simple manner, namely by removing the sub-atmospheric pressure in the vacuum grooves.

In another embodiment of the device the cylindrical collar is closed by a flexible diaphragm on the side of the end face.

Said flexible diaphragm constitutes an 70 extra support over the entire surface of a substrate sucked on the end face on the collar This is of particular importance if a substrate having a central aperture is used in the device according to the invention In a still 75 further embodiment of the device for handling substrates having a central aperture, the above-mentioned diaphragm comprises a central recessed portion and furthermore the mould comprises a central boss, the boss 80 fitting in the recessed portion of the diaphragm.

According to an alternative embodiment of the device for carrying out the method the support plate with mould is situated 85 entirely within the holder of the substrate.

By placing the substrate in the holder an entirely closed system is obtained in which notably the moulding resin provided on the mould is completely protected from ambient 90 influences.

In this embodiment the collar, at its end remote from the substrate, comprises a projecting elastically deformable annular flange which at its free end is connected to a cylin 95 drical jacket which at its end remote from the flange is closed by a bottom portion, the support plate with mould extends from the bottom portion into the space bounded by jacket, flange and collar, the mould being 100 parallel to the substrate and the device comprising a connection if desired, for connecting a vacuum pump, in which, by providing sub-atmospheric pressure in the said space, the substrate is deformed, so as to be 105 spherosymmetrical, and pressed against the mould under elastic deformation of collar and flange.

By way of illustration the invention will now be described in greater detail with 110 reference to the drawing, in which Figure 1 to 3 are cross-sectional views of a device or a part of the device according to the invention in several stages of the method according to the invention carried out with 115 the device, Figures 4 and 8 are cross-sectional views of a plastics record carrier manufactured by means of the method according to the invention 120 Figures 5 to 7 are cross-sectional views of another embodiment of the device according to the invention in various stages of the method according to the invention carried out with the device, 125 Figures 9 to 11 are cross-sectional views of still another embodiment of the device according to the invention also in various stages of the method carried out by means of the device 130 1 581 511 Reference numeral 1 in Figure 1 denotes a support plate for a nickel mould 2 of which the surface remote from the support plate 1 comprises a spiral-like information track.

Provided centrally on the mould 2 is a quantity 3 of a UV-curable moulding resin with acrylic acid ester as the base material The support plate 1 is placed on a stand-table 5 by means of adjusting pins 4 The position of the support plate 1 relative to the standtable 5 can be adjusted by means of the adjusting pins Stand-table 5 comprises a column 6 which has an overhead arm 7 A linear motor 8 is secured to the overhead arm 7 which motor 8 has a shaft 9 which can be moved in the directions shown in Figures 1 and 2 by the motor 8 Shaft 9 comprises on its side remote from the motor a holder 10 for a flexible substrate 11 Holder 10 comprises a cylindrical collar 12 manufactured from deformable material, for example rubber, which at its end face remote from the holder 10, has an annular suction cup 13.

Collar 12 has a perforation 14 which at one end extends into the suction cup 13 and at the other end passes through the holder 10 connected to the collar 12 Via the perforation a sub-atmospheric pressure can be provided in the suction cup 13 by means of a vacuum pump, not shown, as a result of which the flexible circular substrate plate 11 which is manufactured from a material which passes UV light, for example, polymethylmethacrylate, known under the trade name as Plexiglass (a registered Trade Mark), is sucked against the collar 12 via the suction cup 13 Holder 10 has a second perforation 15 extending into a space 16 which is bounded by holder 10, collar 12 and substrate 11 and which otherwise is air-tight An elevated pressure is realized in space 16 via perforation 15 which can be made to communicate with a pressure pump, not shown.

The method according to the invention may be performed as follows.

As a result of a positive pressure provided in space 16, the flexible substrate 11 will be vaulted or deformed spherosymmetrically with simultaneous elastic deformation of collar 12 with sucker 13.

The assembly of holder 10 with collar 12, sucker 13 and spherosymmetrically vaulted substrate 11 sucked thereon is moved by the motor 8 in the direction of the support plate 1 with mould 2 and moulding resin 3 present below the substrate 11 The central portion of the spherosymmetrically vaulted substrate 11 will contact the moulding resin 3 first When the holder 10 with substrate 11 is further lowered, the moulding resin will be rolled by the vaulted substrate over the mould 2, the moulding resin spreading over the mould with a circular fluic front and the spherosymmetrically vaulted substrate being simultaneously deformed, that is flattened.

Figure 2 shows the situation in which the moulding resin is spread partly over the surface of the mould The reference numerals used in Figure 2 correspond to those of Fig 70 ure 1.

It is to be noted that upon rolling the moulding resin the hydraulic resistance of the layer of moulding resin which is inversely proportional to the third power of 75 the thickness of the layer of moulding resin corresponds to the elastic resistance force of the deformed substrate.

When the substrate 11 has been deformed substantially entirely to form a plane surface 80 and the fluid front has nearly reached the edge of the mould, the substrate 11 is uncoupled from collar 12 with sucker 13 in that air is admitted to the sucker 13 via perforation 14 so that the applied sub 85 atmospheric pressure is removed Upon uncoupling, the substrate 11, as a result of its natural stress relief, will engage entirely flatly against the surface of the mould and stow the fluid front of the resin 3 up to the 90 edge of the mould Via the substrate 11 which engages the moulding resin 3 without stress, the layer of moulding resin is cured by exposure to ultraviolet light originating from light source 17 (Figure 3), for exam 95 ple, ultraviolet light of 350 nm originating from a 500 watt water-cooled high pressure mercury lamp The exposure time depends, for example, on the thickness of the layer of moulding resin which may vary from 0 2 to 100 300,am, but is preferably 1-75 jtm, on the composition of the moulding resin, on the light intensity and on the thickness of the substrate which as a rule is from 1-3 mm.

Generally the exposure time will vary from 105 a few seconds to a few minutes.

After curing, in which the substrate 11 is bonded to the moulding resin 3, the resulting plastics record carrier is removed from the mould Figure 4 shows the plastics 110 record carrier which consists of the cured layer of moulding resin 18 having an information pattern and the substrate plate 11 bonded thereto.

Usually, the plastics record carrier is pro 115 vided on the side of the layer of moulding resin comprising the information with a 300 A thick A 1 layer (not shown in Figure 4) which is vapour-deposited in a vacuum bell at a pressure of 10 to 10-5 Torr Finally, a 120 protective lacquer layer (not shown in Figure 4) is provided on the Al layer by pouring nitrocellulose lacquer on the A 1 layer and centrifuging the assembly, the nitrocellulose lacquer spreading as a thin layer over 125 the Al layer.

Reference numeral 19 in Figure 5 denotes a support plate for a nickel mould 20 which has a central pin 21 An annular quantity 22 of a UV-curable moulding resin is provided 130 1 581 511 on the metal mould 20 around the pin 21.

Support plate 19 is secured to stand-table 24 in an adjustable manner by means of adjusting pins 23, the stand-table comprising a column 25 with an overhead support arm 26 A linear motor 27 having a movable shaft 28 is secured to support arm 26 At its end remote from the motor 27 the movable shaft 28 is connected to a holder 29 for the flexible substrate 30 Holder 29 has a flexible cylindrical collar 31 which, at its end remote from the holder, has a widening 32 in which a vacuum duct is provided At its end remote from the holder 29, collar 31 is closed by a flexible diaphragm 34 which is mainly circular and has a central recessed portion 35 In this manner, an air-tight space 39 is formed between holder 29, collar 31 and diaphragm 34, in which space an excessive gas pressure can be provided by suitable means, for example a pressure pump, which are not shown in the Figure, via a perforation 36 Holder 29 comprises a second perforation 37 extending through collar 31 into vacuum duct 33 By communicating holder 29 with a vacuum pump not shown, a sub-atmospheric pressure can be produced in duct 33 via perforation 37.

As a result of said sub-atmospheric pressure the edge of the flexible substrate 30 is sucked against the widened portion 32 of collar 31 The flexible substrate 30 which has a central aperture 38 the dimension of which corresponds to the inside dimension of the central recessed portion 35 of diaphragm 34, will engage the non-recessed portion of diaphragm 34 The substrate 30 is manufactured UV-passing plastics, for example polymeth ylmethacrylate (Plexiglass).

The operation of the device is as follows.

As a result of a positive pressure applied in space 39, the diaphragm 34 and the substrate 30 engaging it will be deformed spherosymmetrically The assembly of holder 29, collar 34 and the spherosymmetrically vaulted diaphragm 34 with substrate is moved in the direction of the mould 20 with moulding resin 22 by means of motor 8 The part of the substrate 30 adjoining the circular aperture will first contact the annular quantity of moulding resin 22 which is situated around pin 21 on the mould 20.

Substrate 30 with aperture 38 will centre around pin 21 The diameter of pin 21 corresponds to the diameter of aperture 38 and also to the inside diameter of recessed portion 35 of diaphragm 34 When the holder 29 with diaphragm 34 and substrate 30 is further lowered, the moulding resin 22 will be rolled over mould 20 by means of the vaulted substrate 30 and spread over the surface of mould 20 with a circular fluid front Deformation, that is flattening of the spherosymmetrically vaulted diaphragm 34 and substrate 30, will take place while furthermore pin 21 extends via aperture 38 of substrate 30 in recessed portion 35 of diaphragm 34.

Figure 6 shows the situation in which the 70 moulding resin 22 is partly spread over the surface of the mould The reference numerals used in Figure 6 correspond to those of Figure 5.

When the fluid front of moulding resin 22 75 has nearly reached the edge of mould 20 and the diaphragm 34 with substrate 30 has nearly been deformed to a plane surface, air is admitted via performation 37 so that the sub-atmospheric pressure in the duct 33 is 80 removed As a result of this the substrate 30 will be uncoupled from holder 29 and the substrate, as a result of natural stress relief, will be stretched entirely and engage mould in a plane surface The resin 22 is rolled 85 entirely onto the edge of the mould 20.

The moulding resin 22 is cured with UVlight from light sources 40 via substrate 30 (Figure 7) The exposure is carried out in the same manner as described with refer 90 ence to Figure 3 It is to be noted that the support plate, the mould and the substrate preferably have the same outside diameters so that the excess of moulding resin after curing can easily be cut away without 95 damaging the layer of resin between mould and substrate.

The resulting assembly of substrate 30 and the cured layer of moulding resin 42 having an information track 41 (Figure 8) 100 thereon is removed from the mould after curing This removal may be carried out, for example, by placing the widened end 32 of collar 31 against the assembly, then providing a sub-atmospheric pressure in vacuum 105 duct 33 so that the assembly is sucked against collar 31, and then raising the holder 29 by means of the linear motor 27 so that the assembly connected to holder 29 via collar 31 is pulled from mould 20 110 Figure 8 shows the resulting plastics information carrier in which substrate 30 is bonded to the cured layer of moulding resin 42 which has an information pattern 41 The plastics record carrier has a central aperture 115 43 Reference numeral 44 in Figure 9 denotes a holder for substrate 45 The holder comprises a circular bottom portion 46 which is connected at its edge to an upright cylindrical jacket 47 At its end remote from 120 bottom portion 46 the jacket 47 has an inwardly directed flange 48 which in turn comprises at its free end an upright collar 49 At its end face the collar 49 has an annular vacuum duct 50 in which a sub 125 atmospheric pressure can be provided via perforation 51 and by means of the vacuum pump not shown The perforation extends from the vacuum duct 50 axially through collar 49, then radially through flange 48 130 1 581 511 and jacket 47 and opens into the outer surface of jacket 47.

Substrate 45 is sucked against the end face of collar 49 by using a sub-atmospheric pressure in duct 50 An air-tight space 52 is enclosed by substrate 45, collar 49, flange 48, jacket 47 and bottom 46 A support plate 53 of mould 54 is accommodated in space 52 The support plate 53 has a flange portion 55 which bears on bottom portion 46 The diameter of flange portion 55 corresponds to the inside diameter of jacket 47.

The mould 54 which is provided on the support plate 53 and which is parallel to substrate 45, is provided centrally with moulding resin 56 A sub-atmospheric pressure can be provided in the said air-tight space 52 via perforation 57 by means of a vacuum pump, not shown.

The method according to the invention carried out by means of this device runs off as follows.

A sub-atmospheric pressure is provided in space 52 via perforation 57 As a result of this, the substrate 45 which is sucked against collar 49 will be deformed spherosymmetrically with simultaneous elastic deformation of collar 49 During said deformation the central portion of substrate 45 will contact the moulding resin 56 present centrally on mould 54 and the substrate 45, when the sub-atmospheric pressure is increased, will then roll the moulding resin over the surface of mould 54 with a circular fluid front Figure 10 shows the situation in which the substrate 45 has spread the moulding resin 55 over a part of mould 54.

The reference numerals in Figure 10 correspond to those of Figure 9.

in the further continuous increase of the sub-atmospheric pressure in space 52, elastic deformation of the flange 48 takes place so that the assembly of substrate 45 with collar 49 and flange 48 is moved in the direction of mould 54 As a result of the increased pressure of the substrate 45 on the mould with moulding resin 56, the moulding resin will be further spread over the mould.

It will be obvious that during rolling the resin 56, the vaulted substrate 45 will continuosly be flattened from the centre.

Figure 11 shows the situation in which no further movement of substrate 45, collar 39 and flange 48 takes place The substrate 45 has been fully flattened and bears against the moulding resin 56 which is spread over the whole mould surface In this situation the layer of moulding resin 56 is exposed to ultra-violet light from light sources 58 and is cured By gradually removing the subatmospheric pressure in space 52, flange 48 and collar 49 will gradually return elastically to the original position in which the substrate 45 with the cured layer of moulding resin 56 bonded thereto is released from the mould surface Finally the sub-atmosphericpressure in duct 50 is removed and the resulting plastics record carrier can be removed from the holder 54 As already stated above, the resulting record carrier 70 may be provided with a reflecting layer and a protective lacquer.

Claims (1)

1. WHAT WE CLAIM IS:-

   1 A method of manufacturing a plastics record carrier having a stratified structure in 75 which a layer of a moulding resin in fluid form is provided on a surface of a mould having an information track thereon, a flexible substrate is provided on the layer of moulding resin, the layer of resin is cured 80 and the assembly of substrate and cured layer of resin connected thereto is removed from the mould, characterized in that the flexible substrate which has been or is in the process of being vaulted spherosymmetri 85 cally, is pressed against the moulding resin provided centrally on the mould, the moulding resin thereby being rolled out over the surface of the mould with a circular fluid front and the vaulted substrate thereby 90 being redeformed to finally form a plane surface, the moulding resin being cured and the assembly of substrate with attached layer of cured resin being removed from the mould 95 2 A method as claimed in Claim 1, characterized in that, when the circular fluid front of the moulding resin is approaching the edge of the mould and the spherosymmetrically vaulted substrate is nearly rede 100 formed to form a plane surface the substrate is uncoupled from the pressure force so that the substrate pushes the fluid front towards the edge of the mould and engages the layer of resin without stress 105 3 A method as claimed in Claim 1 or 2, characterized in that the vaulted substrate is pressed against the moulding resin which has been deposited centrally on the mould in the form of a ring 110 4 A method as claimed in Claim 3, characterized in that the vaulted substrate has a central aperture, the diameter of the aperture corresponding to or being smaller than the inside diameter of the annular layer 115 of resin deposited on the mould.

   A method as claimed in any of the preceding Claims, characterized in that starting material is a plane substrate which is in the form of a circle or ring, and is 120 deformed spherosymmetrically by flexibly suspending or supporting the substrate along its whole circumference and then providing a different gas pressure on both sides of the substrate 125 6 A method as claimed in Claim 5, characterized in that the difference in gas pressure is variable and also forms the force with which the spherosymmetrically vaulted substrate is pressed against the layer of 130 1 581 511 moulding resin.

   7 A method as claimed in any of the preceding Claims, characterized in that a radiation-curable moulding resin is used which is exposed via the substrate after having been rolled out completely over the mould.

   8 A method as claimed in any of the preceding Claims, characterized in that a mould is used of which at least the surface comprising the information track is manufactured from metal.

   9 A device when used in the method as claimed in claim 1 in which the device comprises a holder for the flexible substrate, a support plate for the mould as well as a power source to move the holder or part of the holder relative to the support plate, characterized in that the holder comprises an elastically deformable cylindrical collar which at its annular end face remote from the holder has means to connect the substrate to the said collar along the circumference in a detachable and air-tight manner.

   10 A device as claimed in Claim 9, characterized in that the end face of the collar has one or several vacuum grooves in which a sub-atmospheric pressure can be penerated so that the substrate is sucked against the collar.

   11 A device as claimed in Claim 9 or 10, characterized in that the cylindrical collar is closed by a flexible diaphragm on the side of the end face.

   12 A device as claimed in Claim 11, characterized in that the diaphragm has a central recessed portion and the mould furthermore has a central boss, the boss fitting in the recessed portion of the diaphragm.

   13 A device as claimed in any of the Claims 9 to 12, characterized in that at its end remote from the substrate the collar has a projecting elastically deformable annular flange which at its free end is connected to a 45 cylindrical jacket which at its end remote from the flange is closed by a bottom portion, the support plate with mould extends from the bottom portion into the space bounded by the jacket, flange and collar, 50 and mould being parallel to the substrate and the device comprising a connection if desired for connecting of a vacuum pump, the substrate being deformed spherosymmetrically by app ying a sub-atmospheric 55 pressure in the said space and being pressed against the mould under elastic deformation of collar and flange.

   14 A record carrier obtained according to the method as claimed in any of the 60 Claims 1 to 8.

   A method of manufacturing a plastics record carrier substantially as hereinbefore described with reference to Figures 1 to 11 of the accompanying drawings 65 16 A device for carrying out the method according to Claim 1 substantially, as hereinbefore described with reference to Figures 1 to 3, 5 to 7 or 9 to 11 of the accompanying drawings 70 17 A record carrier substantially as hereinbefore described with reference to Figure 4 or 8 of the accompanying drawings.

   R J BOXALL, Chartered Patent Agent, Berkshire House, 168-173, High Holborn, London WC 1 V 7 AQ.

   Agent for the Applicants.

   Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd, Berwick-upon-Tweed, 1980 Published at the Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.